This invention relates to compositions comprising a polymercaptan which has at least two mercaptan (--SH) groups, a compound which has at least two, and preferably at least three, ethylenically-unsaturated double bonds, and another ethylenically unsaturated compound which contains at least one free carboxyl group. It also relates to the polymerisation of such compositions by means of actinic radiation and/or heat-activated free-radical catalysts, and to the use of the polymerised products as surface coatings, as adhesives, and in reinforced composites, but particularly in printed circuits.
In European Patent Application No. 0031305 we have described polymerisable compositions comprising
(1) a compound containing in the molecule both PA0 (2) a compound containing, per molecule, at least two mercaptan groups directly attached to aliphatic carbon atoms, in a proportion as to supply at least 0.8 such mercaptan group per group selected from allyl, methallyl and 1-propenyl groups in (1) but less than 1.0 such mercaptan group per group selected from acryloyl, methacryloyl, allyl, methallyl, and 1-propenyl groups in (1). PA0 (a) a compound containing in the molecule PA0 (b) a compound containing in the molecule PA0 (c) a compound containing, per molecule, at least two mercaptan groups directly attached to an aliphatic carbon atom or atoms, in a proportion as to supply at least 0.8 such mercaptan group per group selected from allyl, methallyl, and 1-propenyl group in (a) but less than 1.0 such mercaptan group per group selected from acryloyl, methacryloyl, allyl, methallyl, and 1-propenyl groups in (a) with (b). PA0 2,2-bis(3-allyl-4-(methacryloyloxy)phenyl)propane, bis(3-allyl-4-(methacryloyloxy)phenyl)methane, 2,2-bis(3-methallyl-4-(methacryloyloxy)phenyl)propane, bis(3-methallyl-4-(methacryloyloxy)phenyl)methane, 2,2-bis(3-(1-propenyl)-4-(methacryloyloxy)phenyl)propane, bis(3-(1-propenyl)-4-(methacryloyloxy)phenyl)methane, and their acryloyl analogues: PA0 2,2-bis(3-allyl-4-(3-(methacryloyloxy)-2-hydroxypropoxy)phenyl)propane, bis(3-allyl-4-(3-(methacryloyloxy)-2-hydroxypropoxy)phenyl)methane, the corresponding bis(3-methally) and bis(3-(1-propenyl)) compounds, and the acryloyl analogues: PA0 2,2-bis(3-allyl-4-(2-(methacryloyloxy)ethoxy)phenyl)propane, bis(3-allyl-4-(2-methacryloyloxy)ethoxy)phenyl)methane, 2,2-bis(3-methally-4-(2-(methacryloyloxy)ethoxy)phenyl)propane, the corresponding bis(3-methallyl) and bis(3-(1-propenyl)) compounds, and the acryloyl analogues: PA0 2,2-bis(3-allyl-4-(2-(methacryloyloxy)-2-methylethoxy)phenyl)propane, bis(3-allyl-4-(2-(methacryloyloxy)-2-methylethoxy)phenyl)methane, the corresponding bis(3-methallyl) and bis(3-(1-propenyl)) compounds, and the acryloyl analogues; PA0 2,6-diallylphenyl acrylate, 2,6-dimethallylphenyl acrylate, 2,6-di(1-propenyl)phenyl acrylate, and the methacrylates; PA0 1,3-diallyl-2-(2-hydroxy-3-(methacryloyloxy)propoxy)benzene and the corresponding 1,3-dimethallyl and 1,3-di(1-propenyl) compounds; PA0 1-allyl-2-(2-methacryloyloxy)ethoxy)benzene, 1-allyl-2-hydroxy-2-(methacryloyloxy)propoxy)benzene, 1-allyl-2-(2-(methacryloyloxy)-2-methylethoxy)benzene, and the corresponding 1-methallyl compounds, and the acryloyl analogues; PA0 1,3-diallyl-2-(2-methacryloyloxy)ethoxy)benzene, 1,3-dimethallyl-2-(2-methacryloyloxy)ethoxy)benzene, 1,3-di(1-propenyl)-2-(2-(methacryloyloxy)ethoxy)benzene, and the acryloyl analogues; PA0 1,3-diallyl-2-(2-(methacryloyloxy)-2-methylethoxy)benzene, 1,3-dimethallyl-2-(2-(methacryloyloxy)-2-methylethoxy)benzene, 1,3-di(1-propenyl)-2-(2-(methacryloyloxy)-2-methylethoxy)benzene, and the acryloyl analogues; PA0 2,2-bis(3,5-dially-4-(methacryloyloxy)phenyl)propane, bis(3,5-diallyl-4-(methacryloyloxy)phenyl)methane, the corresponding bis(3,5-dimethallyl) and bis(3,5-di(1-propenyl)) compounds, and the acryloyl analogues; PA0 2,2-bis(3,5-diallyl-4-(3-(methacryloyloxy)-2-hydroxypropoxy)phenyl)propane, bis(3,5-diallyl-4-(3-(methacryloyloxy)-2-hydroxypropoxy)phenyl)methane, the corresponding bis(3,5-dimethallyl) and bis(3,5-di(1-propenyl)) compounds and the acryloyl analogues. PA0 1-(allyloxycarbonyl)-2,4-bis(3-(methacryloyloxy)-2-hydroxypropoxycarbonyl)b enzene, 1-(allyloxycarbonyl)-2,5-bis(3-(methacryloyloxy)-2-hydroxypropoxycarbonyl) benzene, 1-(allyloxycarbonyl)-2,4-bis(methacryloyloxycarbonyl)benzene, 1-(allyloxycarbonyl)-2,5-bis(methacryloyloxycarbonyl)benzene, the corresponding 1-(methallyloxycarbonyl) compounds, the corresponding 1-(1-propenyloxycarbonyl) compounds, 1-allyloxycarbonyl-2-(3-methacryloyloxy-2-hydroxypropoxycarbonyl)benzene, 1-(methallyloxycarbonyl)-2-(3-methacryloyloxy-2-hydroxypropoxycarbonyl)ben zene, and the corresponding acryloyloxy compounds. PA0 2,2-bis(4-(3-(methacryloyloxy)-2-hydroxypropoxy)phenyl)propane, bis(4-(3-(methacryloyloxy)-2-hydroxypropoxy)phenyl)methane, and their acryloyl analogues. PA0 1,3-bis(3-(methacryloyloxy)-2-hydroxypropoxycarbonyl)benzene, 1,4-bis(3-(methacryloyloxy)-2-hydroxypropoxycarbonyl)benzene, and the corresponding acryloyloxy compounds.
(i) at least one group selected from acryloyloxy and methacryloyloxy groups, PA1 (ii) at least one group selected from allyl, methallyl, and 1-propenyl groups each of which is attached to a carbon atom which forms part of an aromatic nucleus, either directly or through an oxygen atom or an oxycarbonyl group (--OOC--) which is in turn directly attached to such a carbon atom, PA1 (i) at least one group selected from acryloyloxy and methacryloyloxy groups, PA1 (ii) at least one group selected from allyl, methallyl, and 1-propenyl groups, each of which is attached, either directly or through an oxygen atom or an oxycarbonyl group (--OCO--), to a carbon atom which forms part of an aromatic nucleus, PA1 (iii) at least one group selected from acryloyloxy and methacryloyloxy groups and PA1 (iv) at least one free carboxyl group, and PA1 a is an integer of from 1 to 6. PA1 each R.sup.1 denotes an oxygen-carbon bond or a group of formula I or II as defined above, PA1 each R.sup.2 denotes an allyl, methallyl, or 1-propenyl group, PA1 R.sup.3 denotes a carbon-carbon bond, an alkylene or alkylidene group of up to 5 carbon atoms, an ether oxygen atom, a sulphur atom, or a group of formula --CO--, --SS--, --SO--, or --SO.sub.2 --, PA1 each R.sup.4 denotes a hydrogen, chlorine, or bromine atom, or an alkyl group of 1 to 4 carbon atoms, and PA1 each R.sup.5 denotes a group of formula CH.sub.2 .dbd.C(R)COOR.sup.1 -- or an allyloxy, methallyloxy, or 1-propenyloxy group such that at least one denotes a said group of formula CH.sub.2 .dbd.C(R)COOR.sup.1 -- and at least two each denote an allyloxy, methallyloxy, or 1-propenyloxy group, PA1 with the proviso that, in formulae VIII and IX, each --CH.sub.2 -- and R.sup.2 -- group shown in ortho or para to an indicated group CH.sub.2 .dbd.C(R)COOR.sup.1 -- and R.sup.5 --. PA1 R.sup.1 and R.sup.2 have the meanings assigned in formulae III to XII, and PA1 each R.sup.6 denotes a group of formula I or II. PA1 R and a have the meanings assigned in formula I, PA1 R.sup.1 has the meaning assigned in formulae III to VIII and X to XII, PA1 and R.sup.4 has the meaning assigned in formulae VIII and IX. PA1 each of the remaining symbols of R.sup.7 and R.sup.8, and of R.sup.9 and R.sup.10, denotes the residue of an alcohol after removal of an alcoholic hydroxyl group, said residue containing a (meth)acrylloxy group, especially as a (meth)acryloyloxyalkyleneoxy or (meth)acryloyloxyhydroxyalkyleneoxy group. PA1 R.sup.6 has the meaning assigned in formula XIII and XIV. PA1 R.sup.3 has the meaning assigned in formulae III and XII, PA1 R.sup.4 has the meaning assigned in formula VIII and IX, PA1 each R.sup.12 denotes a carboxyl-containing group of formula XIX as defined above, and PA1 each R.sup.13 denotes an alkyl group of 1 to 8 carbon atoms, particularly a methyl or ethyl group, an aralkyl group of 7 to 9 carbon atoms, or an aryl group of 6 to 8 carbon atoms, or the two R.sup.13 together with the attached carbon atom denote a cyclopentane or cyclohexane ring, PA1 with the proviso that, in formula XXIV, each --CH.sub.2 -- group shown is ortho or para to an indicated group CH.sub.2 .dbd.C(R)COOR.sup.12 O--. PA1 R is as defined in formula II. PA1 R.sup.14 represents a group of formula ##STR11## (wherein R.sup.3 is as defined in formulae III and XII and R.sup.13 is as defined in formula XXVI). PA1 R.sup.15 denotes --CH.sub.2 CH.sub.2 -- or ##STR13## R.sup.16 denotes the residue of an at least dicarboxylic acid after removal of both carboxyl groups. PA1 R.sup.18 represents an aliphatic hydrocarbon radical, which may be interrupted in the chain by not more than one carbonyloxy group, and is preferably of from 1 to 4 carbon atoms, PA1 b is an integer of from 2 to 6, PA1 c is zero or a positive integer of at most 3, such that (b+c) is at most 6 (terms such as c(d) being construed algebraically), and PA1 d and e each represent zero or 1, but are not the same. PA1 b has the meaning assigned in formula XXXVII, PA1 R.sup.19 is an aliphatic hydrocarbon radical of from 2 to 10 carbon atoms, and PA1 R.sup.20 denotes --(CH.sub.2)--, --(CH.sub.2).sub.2 --, or --CH(CH.sub.3)--. PA1 d and e have the meanings assigned in formula XXXVIII, PA1 f is an integer of from 1 to 6, PA1 R.sup.21 represents a divalent organic radical, linked through a carbon atom or carbon atoms thereof to the indicated --O-- or --CO-- units, PA1 R.sup.22 represents a divalent organic radical, linked through a carbon atom or carbon atoms thereof to the indicated --SH group and --O-- or --CO-- unit, and PA1 R.sup.23 represents an organic radical, which must contain at least one aliphatic --SH group when f is 1, and preferably contains at least one such group when f is 2, linked through a carbon atom or carbon atoms thereof to the indicated adjacent --O-- or --CO-- unit or units. PA1 each R.sup.25 denotes an alkylene group containing a chain of at least 2 and at most 6 carbon atoms between the indicated consecutive oxygen atoms, PA1 R.sup.26 represents an aliphatic radical of 1 to 6 carbon atoms containing at least one mercaptan group, PA1 g is a positive integer, preferably such that the average molecular weight of the polymercaptan is not more than 2,000, PA1 h is zero or 1, PA1 j is zero or a positive integer such that (j+k) is at most 6, and PA1 k is an integer of from 2 to 6, preferably of from 3 to 6. PA1 R.sup.25, g, j, and k have the meanings assigned in formula XL, and PA1 m is 1 or 2. PA1 R.sup.28 denotes a hydrogen atom or a methyl or ethyl group, PA1 n is an integer which has an average value of at least 1, and is preferably such that the average molecular weight of the sulphide is at most 1000, and PA1 either p is zero, in which case q and r are each also zero, or p is 1, in which case q is zero or 1 and r is 1. PA1 R.sup.29 represents --CN, --COOH, --CONH.sub.2, --COOR.sup.30, --C.sub.6 H.sub.5, or --OCOR.sup.30, where R.sup.30 is an alkyl group of one to eight carbon atoms, PA1 t is an integer of at least one, PA1 u is zero or a positive integer, and PA1 s is an integer of more than one, preferably such that the average number molecular weight of the polymercaptan is not more than 1000. PA1 each R.sup.13 has the meaning assigned in formula XXVI, PA1 each R.sup.20 has the meaning assigned in formula XXXVIII, and PA1 R.sup.31 denotes a group --OCR.sup.20 SH or a hydrogen atom.
The compositions are polymerised by exposing them to actinic radiation or to the effect of a free-radical catalyst.
In the so-called negative resist method for the production of printed circuits by means of photopolymerisation it is conventional to coat a substrate with a photopolymerisable composition and to expose the coated substrate to actinic radiation through a negative with substantially transparent and substantially opaque areas so that polymerisation takes place in the areas of the coating which have been struck by radiation. Alternatively, such exposure can be carried out using computer-controlled laser beams instead of such a negative. Then the image is developed by dissolving away with a suitable solvent the areas where polymerisation had not occurred, i.e., those areas which had not been struck by actinic radiation. Subsequently, the substrate, usually of copper, may be exposed to etching liquids so that areas not protected by the layer of photopolymerised composition are etched. In further processing, such as in the manufacture of multilayer boards, the layer of photopolymerised composition may have to be removed, generally by mechanical means.
Disadvantages of processes presently employed are that organic solvents are often used for development, with associated risks due to toxicity and flammability, and that mechanical processes for removing the photopolymerised composition may cause damage to the printed circuit.
In the process of this invention there is used a polymerisable composition which also contains carboxylic acid groups; if exposure to actinic radiation is effected as through a negative with substantially opaque areas, it is possible to remove the composition from unexposed zones by treatment with an aqueous alkaline solution, due to salt formation on the carboxylic acid groups. Use of an organic solvent for this purpose, with its attendant disadvantages, is therefore avoided. A further advantage is that the polymerised composition can be subsequently removed if desired by use of more strongly aqueous alkaline solutions.